The rosy gene in Drosophila melanogaster codes for the enzyme, xanthine dehydrogenase. A large number of mutants, including some which have the characteristics of regulatory mutations, exist in the rosy gene. Efforts are directed at analyzing the XDH protein from various mutants, and at the isolation of the messenger RNA for this protein, with the aim of correlating structural changes in the genes with the known genetic map. Current work is also directed at an analogous genetic and biochemical analysis of the gene coding for paramyosin in the nematode, Caenorhabditis elegans. The paramyosin molecule is being studied by peptide mapping and two-dimensional gel electrophoresis, and mRNA is being fractionated in order to purify the paramyosin message.